The purpose of this research is to provide information on the mode of action of nerve growth factor. Nerve growth factor is required for the development and maintenance of the sympathetic nervous system and may be prototypic for factors involved in differentiation of various cell types. The mechanism of action of nerve growth factor is of interest because it will lead to an understanding of the way in which gene expression is regulated in neurons and how such factors induce the synthesis of specific enzymes for the biosynthesis of the neurotransmitter, norepinephrine. In turn, such information may lead to an understanding of the development and differentiation of the non-dividing, non-replaceable neurons of the central nervous system, and to information about the tumors that arise from them.